Switchboard plug



April 27, 1948. H. c. CALVIN SWITCHBOARD PLUG Filed sept. 5, 194s Patented Apr. 27, 1948 UNITED STATE SWITCHBOABDPLUG Harry Cl Calvin, Dothan, Ala.assgnor'offone` fourth to Earle C. Moody, Dothan,` Ala.

Appucanmseptember 3, 194s, serial ivaA 501,171

`sY clams. (o1. 173-361) 1. This invention f'relates to flexiblev electrical plugs, and more particularlyto` a-` flexible telephone switchboard plug. i

The conventional switchboard'plug` comprises a substantially elongated body havingy tip,- ring and sleeve contacts -engageable withcoacting contacts in the switchboard jack openings, and a flexible cable extends tothe-plug and-contains three wires connected 1 to the 4vrespective contacts referred" to.v TheV flexible. cable, uponinsertion of the pluginto the jack, issubjected tothe force of the operators ngersor palintopushthe. plug into position, and thisforce causes-the. covering of the cable to out andbreak against the base of the plug therebyexposilflg the conductors therein. This puts thezentire strainon .the conductors themselves which, sooner or later, `weakens the conductors to the breaking-point. When the-plug is pulled` and dropped Vto `its normal position the cable tends to` straiehte'ntoi a` position: in alignment with theplug, This constant bending and straightening or the cable aegravatesithe. condition referred to. and accelerates crystallization and breaking of the` wires infthei cable, thus requiring the `repairing ofthe electrical connections.

An important objectof'the present r invention is to provide a novel flexibleelectrical plug, and more particularly a telephone `switchboardl plus. wherein the bending of the cable. relative tothe plug is limited and wherein thecablefis vrelieved of the pressure usually exertedthereagainst by the' operator.

A further objectistoprovide such anarrangement wherein thel cable extends: through a'thimble pivoted tothe body of the plus-landengaeeable therewith to limit the turning movement of the thimble relativ'eto theplugiand thus limit the bending'ofthe cable.

A further object is to: provide a telephone switchboard plug of the type referred tov wherein the-pivoted thimbleiszutilized for the grounding or the wire` usually?" connected tothe `sleeve contact of the p1us,thus completely eliminating` the bendingv of.' one `of.` the three 1 wires-i employed l. in connection with. aplugfor this character.

A` further object is to provide such` a device wherein a pivoted thimblc; isi ribbed ori threaded internally for engagement with the cable to iix the latter firmly-with respect-.to the` cable, thus effectively securing` the` parts together and at thesame time preventingthe pulling of `thecable from exerting a pullonfthe `wires and their-connections with theassooiatedcontact elements.

Other objects andadvantages of thefinvention will become apparent during` the course f of the following description.

In the drawing I' have shown one embodiment of the invention. i Inthis showing:

Figurel isa perspective view of the device shown in. conjunction with a portion of a telephone switch board,-

Figure 2 isa side elevation-of` the device showing the-thimble in thelturnedposition it assumes when the plug isinserteddntheljack, parts beine.r broiken away andparts being-shown in section, an

Figure 3 is-an enlarged sectional view ofthe sleeve and a. portion of the plug, parts being shown in elevation.` l

Referring` tothe drawinegthe numeral Ill designates a conventional telephone switchboard having jackopenings` II= inf` which isi insertable a plugiindicate'd as a whole by the numeral I2. This plug isprovlded-withlthe usual tipcontact I3,- ring-contact.v I4 and sleeve. contact l5'` which are engageable' with'thethree conventional jack contacts to complete thenecessarytelephone circuitsi Theprojecting portionof the plus carrying the threecontactsreferredto is carriedby a fiber orsixnilarrbodyjf I 6. Three'wires, toibe referred to later, extend; through this body for connection with the respective contacts lil,V lo andlsa The elements described'mayabe conventional in everyway, and in the usual switchboard plug, the three wires, arranged in a cable',extend directly from the body I6 and downwardly at ani angle, whenthe plug iis-.insertecl. It is the downward bendingoflthe Wires which results :in their breaking, and itis this dlsadvantageous result which is overcome by` the' present' construction. The body ldisprovided withaV preferably metallic ferrule I 'l having its endlremote from the body I6 Acut away atdiametrically opposite pointskas at I8 with the intermediatepoints l9extendng longitudinally from the body |6.l

Thev extended portions I9 of l'fhefer'rulev l'l are pivotally connected preferably by shouldered lscrews. 20 kwith .arms 2l having their adjacent ends arranged outward-1yof. and contacting` the ferrule Il. The other ends of the arms 21| .are

soldered, brazed or otherwise permanently con- -sagement of the inner edge portions or the 1,tniinblelwitlc the edgesof .either ofthe cut-away portions of the ferrule I1, as indicated in Figure 2.

'Ihe cable for the wires is indicated by the numeral 23, and this cable contains three wires 24, 25 and 25, and the wires 24 and 25 extend through the body I6 and through the sleeve I5 for connection with the respective contacts I3 and I4. In conventional constructions the third wire 26 extends through the body I 5 for connection with the contact I5. In the present instance, however, the cable 23 terminates short of Y the inner end of the thimble 22 and a short end of the wire 26 is stripped as at 21 and soldered to the thimble 22 to be thus grounded thereon. This thimble Will' be electrically connected, of course, to the ferrule I1 through the arms 2|. The ferrule I1 is integral with or permanently connected to a sleeve I1', forming a part of the sleeve contact I5. Accordingly, the soldering of the wire end 21 establishes electrical connection between such element and the sleeve contact I5.

In order to rigidly secure the cable 23 to the thimble 22 so that any pull on the cable will be transmitted directlyto the thimble and not to the wires 24, 25 or 26 the interior of the thimble 22 is ridged as at 28 (Figure 3). These ridges are preferably in the form of threads Which will embed themselves in the cable covering` and thus afford an effective mechanical connection between the cable 23 and thimble 22.

The operation of the device will be apparent from the foregoing description. As previously statedth e cable 23 ordinarily projects directly from the body of the plug l2, and'extends downwardly at an angle therefrom when `the plug is inserted into the jack, orv is arranged horizontally in a position for such operation. In pushing the plug into the jack, the operator usually presses against the cable at the point where the bend occurs therein, and this pressure tends to cut the cable covering and place the entirestrain on the conductors. This, together with the bending of the wires at each insertion of the plug, causes the wires to crystall lize and break after relatively short use.

In the present device, the thimble y22 limits the bending of the wiresand forms arigid finger piece against which the operator may push in inserting the plug, instead of pushing directly on the cable. Thus the wires are relieved of the destructive force ordinarilyv exerted thereagainst by the operator,

Moreover, the thimble Iis advantageous for two other reasons. In the rst place it limits the bending of the wires, the parts being designed so that the thimble 22 preferably cannot turn to an angle of greater than 45 with respect to the plug. Y This limiting of the bending of the wires also lengthens the life of the wires by minimizing crystallization of the metal ofthe wires which occurs incident to bending. In the second -place the thimble 22 penmits the third wire 26 to be electrically connected to its associated :contact I without having to extend from Vthe thimble 22.' Tl'ierefore, the bending of one of the wires is eliminated completely, and more space is provided for the remaining two wires. The latter fact eliminates crowding of the Wire at the points where they bend, and permits the wires to partake of freer movement without sharp bending. The various features of the device, therefore, obviously cooperate to greatly-lengthen the life of the wires.

It is to be'understood that the form of the invention herewith-shown and describedis to be ,4 taken as a preferred example of the same and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subj oined claims.

I claim:

l. A flexible electrical connection plug comprising a plug bodyhaving a plurality of contacts at one end portion thereof, a cylindrical ferrule carried by said body at the opposite end thereof, said ferrule having diametrically opposite portions projecting longitudinally therefrom as continuations thereof, a cylindrical thimble substantially equal in diameter to and normally arranged in axial alignment with said ferrule and provided with diametrically opposite portions projecting longitudinally -therefrom and each lying radially outwardlyof and contacting with one of the projecting portions of said ferrule, the adjacent ends of said thimble and said ferrule being open and unobstructedl for the passage ofV wires therethrough, and a pivot pin projecting thrbughjeach projecting portion of said thimble and the corresponding projecting portion :of vsaid ferrule to pivotally connect said thimble and said ferrule to each other, the wires engaging against the inner said thimble swings about the pivot axis of said pins relative to said ferrule, the contacting surfaces of the projecting portions of said ferrule and said thimble forming the sole frictional contact between said thimble and said ferrule during turning movement thereof relative to each other.

2. A telephone switchboard plug comprising a plug body having a pluralityV of contacts at one end portion thereof and an open ended cylindrical ferrule at the other end thereof,rsaid ferrule having diametrically opposite portions projecting longitudinally therefrom as continuations thereof, an open ended cylindrical'thimble substantially equal in diameter to said ferrule and'normally arranged in axial alignment therewith, a pair of parallel arms fixed to said thimble diametrically opposite each other, said arms extending longitudinally of said thimble' and overlying the projections of said ferrule radially outwardly thereof and in contact therewith, the adjacent open ends of said ferrule and said.V thimble being unobstructed for the passage of wires therethrough, and a pivot pin projecting through each arm and the corresponding projection of said thimble,said pins being in axial alignment to pivotally connect said thimble and said ferrule to each other and the contacting surfaces of said arms and the projections of said thimble constituting the sole frictional engagement between said ferrule and said thimble during relative turning movement thereof about said axis, said thimble and said vferrule being adapted for the passage therethrough of wires engageable with the inner surface of said ferrule to be bent thereby when said thimble is turned about said axis relative to said ferrule;

3. A telephone switchboardplug comprising a plug body having a plurality of contacts at one end portion thereof and an open ended cylindrical ferrule at the other end thereof, said ferrule having diametrically opposite portions projecting longitudinally therefrom as continuations thereof,

an open ended cylindrical thimble substantially 5 of and in contact therewith, the adjacent open ends of said ferrule and said thimble being unobstructed for the passage of wires therethrough, and a pivot pin projecting through each arm and the corresponding projection of said thimble, said pins being in axial alignmentl to pivotally connect said thimble and said ferrule to each other and the contacting surfaces of said arms and the projections of said thimble constituting the sole frictional engagement between said ferrule and said thimble during relative turning movement thereof about said axis, said thimble and said ferrule being adapted for the passage therethrough of wires engageable with the inner surface of said ferrule to be bent thereby when said thimble is turned about said axis relative to said ferrule, the ends of said thimble between the projections thereof being engageable with the adjacent ends of said ferrule to predetermine and limit relative swinging movement of said ferrule and. said thimble about said pivot axis.

HARRY C. CALVIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 836,805 Dozier Nov. 27, 1906 886,262 Smith Apr. 281, 1908 1,038,070 Benjamin Sept. 10i, 1912 15 1,104,195 Janes July 21, 1914 1,268,812 Beck June 11, 1918 2,274,357 Bryant et a1 Feb. 24, 1942 

